Perovskite Solar Cells Using Surface‐Modified NiOx Nanoparticles as Hole Transport Materials in n‐i‐p Configuration

Modified NiO x nanoparticles (NPs) developed via surface engineering are applied to a hole transport layer (HTL) in n‐i‐p‐structured perovskite solar cells (PSCs). Hexanoic acid (HA) as a surfactant improves the dispersibility of NiO x NPs in chlorobenzene (CB). The conductivity of the NiO x ‐HA film is , which is superior to that of 2,2′,7,7′‐tetrakis( N,N ‐di‐ p ‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) with dopants. The NiO x ‐HA film shows better hole extraction properties compared with the pristine NiO x film. The NiO x ‐HA NPs form closely packed and pinhole‐free films, leading to improved device performance with a power conversion efficiency from 5.5% to 13.1%.